KR20120107046A - Process for recovery of noble metals from functionalised, noble metal-containing adsorption materials - Google Patents

Abstract

PURPOSE: A collecting method for precious metals from functionalized precious metal containing adsorbent materials is provided to effectively separate the precious metals from functionalized scavengers by dissolving the scavengers in an oxidized acid solution. CONSTITUTION: A collecting method for precious metals from functionalized precious metal containing adsorbent materials comprises the following steps: providing precious metal-containing composition which includes adsorbent; obtaining a composition by ashing the precious metal containing composition; obtaining precious metal contained residue by dissolving a part of the precious metal containing residue in the oxidized acid solution; and collecting the precious metal by reducing the precious metal salt. In the first step, the adsorbent is set as a base material and is functionalized by organic group. In the second step, the carbon residue content is adjusted under 10wt% based on the total weight of the precious metal containing composition after ashing.

Description

PROCESS FOR RECOVERY OF NOBLE METALS FROM FUNCTIONALISED, NOBLE METAL-CONTAINING ADSORPTION MATERIALS}

The present invention relates to a method for recovering a noble metal from a noble metal-containing composition.

In many industrial processes, noble metal-containing residues are obtained that are sufficiently high in noble metal content to be economically inexpensive to recover. Examples of such residues are slurries, suspended solids, abrasive dust, production wastes containing noble metal-containing catalyst residues discarded from the plant.

Many methods are known for recovering precious metals contained in the composition. One method that is very tolerant and characterized by very high efficiency is the so-called cyanide leaching method, in particular used to recover gold. In this regard, sodium cyanide and potassium leachate are added to the gold-containing composition to dissolve the gold and some other precious metals contained therein in the leachate. In the case of gold, it is bound as an ionic complex in aqueous solution. In the second process step, gold can then be electrolytically precipitated from solution. Although the method is very smooth from a technical point of view, it is associated with the crucial disadvantage of the need to deal with large quantities of highly toxic cyanide, which is very problematic for reasons of environmental protection and the health of the person responsible for this task. .

In order to avoid this problem, attempts have been made to avoid this by using other complexing agents, for example thiourea. This approach, however, is particularly associated with the problem that colloidal sulfur, which rapidly reduces process efficiency, forms and rapidly passivates the surface of the metal particles to be dissolved. Accordingly, methods involving the use of thiourea as a complexing agent have not been economically significant in industrial metal regeneration methods.

Another method for recovering precious metals, for example the method described in WO-A-2006 / 013060, is to use a so-called scavenger material. Silica gel-based or aluminum oxide-based inorganic materials functionalized by organic complexing agents and adsorbing noble metals upon contact with noble metal-containing solutions are commonly used. Next, the adsorbed precious metal is further separated from the thus obtained renewable product. The first step in separating the precious metal from the renewable product is to dissolve the precious metal. For the use of silica gel-based scavenger materials, direct leaching through oxidative acid treatment, as described, for example, in EP-A-1 576 200 or US Pat. No. 4,360,380, is sufficient to quantitatively remove the adsorbed precious metals, which is high enough in silica gel. Not effective A significant amount of precious metal remains in the carrier and cannot be readily dissolved. Treatment of renewable products with complexing agents, such as thiourea, may result in the elution of only some of the precious metal adsorbed on silica gel (" Recovery "). of rhodium-containing catalysts by silica - based chelating ion exchangers containing N and S donor atoms ", Kramer et al ., Inorganica Chimica Acta (2001), vol. 315 (2), pages 183-190).

It is an object of the present invention to overcome the disadvantages of the prior art associated with the separation of noble metals from organofunctional functionalized capture agent materials, in particular silica gel based or aluminum oxide gel based inorganic functionalized by complexing agents.

In particular, it is an object of the present invention to specify a method for separating precious metals from the trapping agent material so that the precious metals can be separated more efficiently than the known methods according to the prior art.

The above-mentioned objects are achieved by a method for recovering a noble metal from a noble metal-containing composition comprising the following process steps:

i) a process for providing a noble metal-containing composition based on an inorganic substance and functionalized by an organic group to contain an adsorbent having at least one precious metal adsorbed thereon;

ii) ashing the noble metal-containing composition provided in process step i) to have a carbon residual content of at most 10% by weight, particularly preferably at most 5% by weight, even more, relative to the total weight of the noble metal-containing composition after ashing Obtaining a calcined composition, preferably adjusted to at most 3.5 wt% or less, most preferably at most 2.0 wt% or less;

iii) a process step of dissolving the assimilated composition obtained in process step ii) at least partially in an aqueous alkali solution to obtain a noble metal-containing residue;

iv) a process step of dissolving the noble metal-containing residue obtained in process step iii) at least partially in an aqueous solution of oxidizing acid to obtain an aqueous solution of salt of noble metal;

v) process step of recovering the precious metal by optionally reducing the precious metal salt obtained in process step iv).

Firstly, process step i) of the process according to the invention involves providing a noble metal-containing composition based on an inorganic substance and functionalized by organic groups and containing an adsorbent on which at least one noble metal is adsorbed.

As functionalized adsorbents based on inorganics, any materials known to those skilled in the art and commonly used as capture agent materials in the recovery of precious metals from industrial wastes can be considered. The materials are preferably inorganic gels based on silicon oxide or aluminum oxide. Particularly preferred adsorbents are those based on silica gel or aluminum oxide gel, and it is particularly preferable to use adsorbents based on silica gel. Particular preference is given here to silica gels functionalized by sulfur- and / or nitrogen-containing organic groups, with silicagels functionalized by thiols or sulfide groups in this regard.

Examples of suitable silica gels functionalized by organic groups are, for example, functionalized silica gels sold under the trade name ISOLUTE® by Biotage AG, Sweden. The silica gel is, for example, silica gel functionalized by 2,4,6-trimercaptotriazine group (ISOLUTE® SI-TMT), silica gel functionalized by carbonate group (ISOLUTE® SI-Carbonate), thiol group, Silica gels functionalized by, for example, 1-propanethiol groups (ISOLUTE® SI-Thiol), silica gels functionalized by triamine groups, such as 3- (diethylenetriamine) propyl groups (ISOLUTE® SI-Triamine), Or silica gels functionalized by sulfonic acid groups, for example silica gels functionalized by ethylbenzenesulfonylhydrazine groups (ISOLUTE® SI-Tosyl Hydrazine), silica gels functionalized by methylbenzenesulfonic acid groups (ISOLUTE® SI-TsOH) Or silica gel functionalized with propylsulfonic acid group (ISOLUTE® SI-Propylsulfonic acid). SilicaBond ^® tradename, PhosphonicS ^TM or functionalized with commercially available ^TM QuadraSil silica gel can also be mentioned. Silica gel functionalized by N-acetyl-L-cysteine group (product number 16-0200) and silica gel functionalized by 2-aminoethyl sulfide-ethyl group in the trapping agent material marketed under the brand name PhosphonicS ^™ (product number 16 -0215), silica gel functionalized by 2-mercaptoethylethyl sulfide group (product number 16-0650), silica gel functionalized by 3-mercaptopropylethyl sulfide group (product number 16-1700, 16-1706) , 16-1702 and 16-1704), silica gel functionalized by pentaerythritol-2-mercaptoacetate-ethyl sulfide group (product number 16-1540) and silica gel functionalized by triamine-ethyl sulfideamide group Particularly preferred is (Product No. 16-0210).

Functionalized silica gel materials of this type each have a particle size range of at least 100 to 1,000 μm, particularly preferably at least 200 to 800 μm, most preferably at least 300 to 600 μm, at least each of the functionalized silica gel materials used. 50% by weight, particularly preferably at least 75% by weight, even more preferably at least 90% by weight, most preferably 100% by weight, are usually used as particulate solids.

Said adsorbents based on inorganic substances, in particular those adsorbents based on silica gel, are functionalized by organic groups of 0.1 to 10 mmol / g, particularly preferably 0.25 to 5 mmol / g, most preferably 0.5 to 1.5 mmol / g. It is common to get angry.

At least one precious metal is adsorbed to the above-mentioned silica gel contained in the composition provided in process step i) and based on an inorganic material and functionalized by an organic group, preferably functionalized by an organic group, wherein in the process step i) The provided precious metal-containing compositions preferably contain at least 0.5% by weight, particularly preferably at least 1.0% by weight and most preferably at least 1.5% by weight, of each of the precious metal-containing compositions provided in process step i). Do. In principle, precious metal-containing compositions containing up to 10% by weight or more of the precious metal can be used in the process according to the invention. In this connection the precious metal-containing composition provided in process step i) is at least 25% by weight, particularly preferably at least 30% by weight, most preferably at least 35% by weight, relative to the total weight of the precious metal-containing composition provided in process step i) It is also preferable to contain% SiO ₂ .

Preferably, the precious metal-containing composition provided in process step i) is brought into contact with an adsorbent functionalized by an organic group and based on an inorganic group, whereby the precious metal-containing residue from which the precious metal can be recovered, preferably the precious metal-containing residue Can be obtained by contacting silica gel functionalized with an organic group. As precious metals, for example, gold, platinum, iridium, palladium, osmium, silver, mercury, polonium, ruthenium, rhodium, copper, bismuth, technetium, rhenium and antimony can be considered, and gold, platinum, iridium, palladium, osmium, silver Ruthenium, rhodium, copper, bismuth, technetium and rhenium are particularly preferred, and platinum and rhodium are most preferred.

The precious metal-containing residue from which the precious metal can be recovered can be for example effluent from mine or electroplating or metallurgical operations. It is also conceivable to use the noble metal-containing catalyst during the organic synthesis and to consider the production residues of the organic synthesis process where at least some of the catalytic material reaches the product phase. In order to adsorb the noble metal through the scavenger material from this type of noble metal-containing residue, a generally particulate material is preferably present in the liquid form and preferably from 60 to 120 ° C., particularly preferably Is contacted in a temperature range of 80 to 100 ° C. For example, the scavenger material is added to the residue with stirring and a mixture of the noble metal-containing residue and scavenger material for a predetermined contact time range, typically 5 minutes to 5 hours, particularly preferably 30 minutes to 2.5 hours. Can be contacted by stirring, after which the scavenger material is separated from the residue. For example, the trapping material loaded with the precious metal may be separated from the residue by filtration, sedimentation or centrifugation. Furthermore, it is conceivable and preferred according to the invention to provide a trapping agent material in the column and to pass the precious metal-containing residue through the column. This is another means of loading precious metals into the trapping agent material.

Typically the precious metal-containing compositions provided in process step i) range from 10 to 50% by weight, respectively, of organic matter from the abovementioned residues in addition to the adsorbent loaded with precious metals relative to the total weight of the precious metal-containing compositions provided in process step i), Especially in amounts ranging from 20 to 40% by weight.

In process step ii) of the process according to the invention, the noble metal-containing composition provided in process step i) is sintered to give up to 10% by weight or less, particularly preferably at most, carbon in each of the total weight of the noble metal-containing composition after incineration. An aerated composition adjusted to 5% by weight or less, even more preferably at most 3.5% by weight or less and most preferably at most 2.0% by weight or less is obtained. In this incineration process, the combustion losses resulting from removing at least some of the functional groups of the adsorbent and other organics which may be present in the composition are preferably at least 40% by weight, particularly preferably at least 45% by weight, most preferably Is at least 50% by weight.

In process step ii) it is preferably at least 2 hours, more preferably at least 4 hours and even more preferably at a temperature of at least 500 ° C, particularly preferably at least 700 ° C, most preferably at least 800 ° C. The incubation is carried out for a period of at least 6 hours, particularly preferably at least 10 hours. Painting in air is common. It is preferable that the incineration temperature does not exceed 1,200 ° C, particularly preferably 1,100 ° C, most preferably 1,000 ° C.

The ingestion of the noble metal-containing composition in process step ii) may optionally include two or more steps as described, for example, in WO 2007/036334. In this connection, the first step involves heating the noble metal-containing composition, for example in the nitrogen atmosphere or in the air atmosphere, for the above-mentioned times, for the first time with the first part of the functional group of the adsorbent and other organics which may be present in the composition. Remove the part. Subsequently, the partially assimilated material may optionally be further mixed and then further heated and optionally further heated, optionally at the above-mentioned temperature conditions, for further reduction of the carbon content. Said further heating is preferably carried out in the presence of oxygen, particularly preferably in an air atmosphere. By the two-step process the painting is carried out in a particularly efficient manner.

Next, in process step iii) of the process according to the invention, the assimilated composition obtained in process step ii) is at least partly dissolved in an aqueous alkali solution to obtain a noble metal-containing residue. In this process step predominantly the inorganics provided in process step i), ie inorganics, preferably based on silica gel, are at least partially dissolved. Said dissolution is a temperature of 50 to 300 ° C., particularly preferably 70 to 200 ° C. while admixing the calcined composition with an aqueous alkali solution, preferably with an aqueous NaOH or KOH solution, particularly preferably with an aqueous NaOH solution, and optionally pressing the resulting mixture. It is preferable to carry out by heating in the range of 30 minutes to 10 hours, particularly preferably in the range of 1.5 to 8.5 hours.

The use concentration of the aqueous alkali solution is preferably at least 10% by weight, even more preferably at least 15% by weight, most preferably at least 20% by weight, based on the total weight of the aqueous alkali solution used in process step iii), usually The concentration range is 20 to 55% by weight.

In this connection it is particularly preferred in process step iii) to dissolve at least a part of the assimilated composition obtained in process step ii) in the presence of a reducing agent in aqueous aqueous solution. Adding a reducing agent during dissolution can prevent the noble metal from dissolving at the initial time.

The reducing agent is preferably an organic reducing agent, hydrazine or hydrogen gas, with a preferred organic reducing agent consisting of formic acid or formate, formaldehyde, alcohol (for example methanol or ethanol), ascorbic acid, glucose, gluconic acid, ascorbic acid and oxalic acid. Selected from the group.

The amount of reducing agent used in process step iii) ranges from 1 mg to 2,500 mg per gram of adsorbed adsorbent, particularly preferably from 5 mg to 1,000 mg per gram of adsorbed adsorbent and most preferably from 10 mg to 100 mg per gram of adsorbed composition. Can be. The concentration range of the reducing agent in the aqueous alkali solution used in process step iii) may be 0.1 to 10% by weight, particularly preferably 0.5 to 5% by weight, relative to the total weight of the aqueous alkali solution used in process step iii).

In addition to the reducing agent, other additives may be added to the aqueous alkali solution, and in the case where the noble metal-containing residue is to be precipitated and separated, it is particularly preferable to separate the aqueous alkaline solution from the precious metal-containing residue by a decanting method by adding a precipitation agent. .

The noble metal-containing residue obtained after dissolving the adsorbent sintered in the manner described above can be separated from the solution, for example, by filtration, sedimentation or centrifugation, preferably by sedimentation, and optionally with water or aqueous solution. After washing, feed to subsequent process step iv). If it is desired to separate the noble metal-containing residue by filtration with filter paper, it may be advantageous to provide an additional process step for removing the filter paper prior to carrying out process step iv).

In process step iv), the noble metal-containing residue is at least partially dissolved (“leached out”) in an aqueous oxidizing acid solution, preferably in an aqueous chloride solution of the precious metal, to obtain an aqueous solution of salt of the precious metal. It can be seen, in particular, if the precious metal to be recovered is rhodium, it is advantageous to further reduce the precious metal-containing residue obtained in process step iii) prior to process step iv), preferably in the hydrogen stream. Preference is given to reducing the hydrogen stream in the temperature range 200 to 600 ° C., particularly preferably 300 to 500 ° C. for 1 to 24 hours, particularly preferably 4 to 10 hours.

The precious metal-containing residue obtained in process step iii) is obtained at least partly in nitric acid as an aqueous oxidizing acid solution, in a mixture containing hydrochloric acid and nitric acid, for example aqua regia, or as an oxidizing agent to obtain an aqueous solution of salt of the precious metal in process step iv). It is preferable to dissolve in hydrochloric acid containing, for example, hydrochloric acid containing chlorine gas or hydrochloric acid containing chlorate. Preference is given to dissolving the noble metal-containing residue in the oxidizing acid in the temperature range 30 to 200 ° C, particularly preferably 60 to 100 ° C. The concentration of the acid used in process step iv) is preferably at least 10% by weight, particularly preferably at least 20% by weight, most preferably at least 30% by weight relative to the total weight of the aqueous solution of oxidizing acid used in process step iv). %to be.

Next, in process step v) of the process according to the invention, the noble metal can optionally be recovered from the noble metal salt obtained in process step iv). The recovery can be carried out in a manner known to the person skilled in the art, for example reduction, for example electrolysis, of the precious metal salt obtained in process step iv). In this connection the noble metal is preferably obtained with a purity of at least 90%, particularly preferably at least 95% and most preferably at least 99%.

Typically one skilled in the art will try to obtain a liquid with as low a noble metal concentration as possible.

For example, if the amount of water in terms of grams in step iii) or the amount of sodium hydroxide solution is about 10 to 15 times the mass of the to-be-treated residue containing 1 to 5% by weight of the precious metal, the concentration of the precious metal is generally 5 Solutions of very low noble metal-containing residues can be obtained at less than mg / l or even below 1 mg / l. This is evident for example from Examples 2 to 4 below. Further treatment of the solution is usually not economical and can be disposed of.

In general, the total mass of the loaded trapping agent material used is observed to decrease by more than 90%, in particular more than 95%, after step iii), which means that the noble metal content of the residue can increase by 20 times.

Hereinafter, the present invention will be described in more detail with reference to non-limiting examples.

Example

Example  One

56.9 g scavenger loaded with 1.60 wt% rhodium (PhosphonicS ^{TM from} Strem Chemicals, USA) Unspecified residues of organic process waste discarded from the homogeneous catalysis process were burned for 8 hours at 800 ° C. in an air atmosphere to remove all organic components. A total of 25.5 g of silica gel-containing ash was obtained, corresponding to a combustion loss of 55%. The carbon residue was 1.6% and the Rh content was 3.56% (0.91 g).

Example  2

25 g of rhodium-containing ash obtained in a similar manner to Example 1 was heated to 180 ° C. for 4 hours in the presence of 250 ml of 45% sodium hydroxide solution and 1 g of sodium formate using a pressurized autoclave. The sample was then allowed to cool and the supernatant decanted out. This supernatant solution contained less than 1 mg / l Rh. The residue on the nutche filter was washed with water and dried. The weight of the concentrated residue was analyzed to be 0.5 g.

Example  3

18.5 g of rhodium-containing ash obtained in a similar manner to Example 1 was heated to 180 ° C. for 8 hours in the presence of 185 ml of 45% NaOH solution and 1 g of sodium formate using a pressurized autoclave. The sample was then allowed to cool and the supernatant decanted out. This supernatant solution contained less than 1 mg / l Rh. The residue on the nutche filter was washed with water and dried. The weight of the concentrated residue was analyzed to be 3.8 g.

Example  4

A total of 25.5 g of rhodium-containing ash obtained by a method similar to Example 1 was added to 350 ml of 31% NaOH solution, dropwise addition of 14 ml 22% hydrazine solution, and the sample was placed at 80 ° C. in an open container. Heated for 3 hours. Thereafter, 50-100 ml of water and 20 ml of settling agent (Praestol®, acrylic acid and acrylamide copolymer, Ashland Deutschland GmbH) were added, the sample was allowed to settle and the residue was decanted out. This residue was filtered and washed with water; The mass after drying was 2 g. The decanted solution contained 3 mg / l rhodium and was discarded.

Example  5

The residue obtained in Example 4 was reduced for 7 hours at 400 ° C. in hydrogen stream, and then leached by introducing chlorine gas for 15 hours in a 60 ° C. device containing 32% hydrochloric acid. During this period, the rhodium-containing hydrochloric acid was replaced once with fresh 32% hydrochloric acid. The hydrochloric acid solution was collected, and the Rh content was measured by ICP, which was 0.91 g Rh.

Example  6

94.9 g of platinum-loaded scavenger (using PhosphonicS ^TM 16-1700 from Strem Chemicals, USA) and unspecified residues of organic process waste discarded from the homogeneous catalytic silicon production process were burned for 8 hours at 800 ° C. in an air atmosphere. All organic components were removed. A total of 48.0 g of silica gel-containing ash was obtained, corresponding to a combustion loss of 49%. The carbon residual was 200 ppm and the Pt content was 1.10% (0.528 g).

Example  7

A total of 20.1 g of platinum-containing ash obtained by a method similar to Example 6 was heated to 80 ° C. for 4 hours in an open vessel in which 270 ml of 31% NaOH solution and 4 ml formic acid were present. This suspension was then cooled to 60 ° C. and filtered. After washing with water, 1.35 g of residue were obtained. As measured by ICP, platinum was not detected in this alkaline filtrate.

Example  8

The residue obtained from Example 7 was leached at 80-100 ° C. in 600 ml of aqua regia and the Pt content was determined by ICP and found to be 0.22 g.

Example  9

A total of 20.2 g of platinum-containing ash obtained by a method similar to Example 6 was heated to 80 ° C. for 3 hours in an open vessel containing 270 ml of 31% NaOH solution and 9 ml of 22% hydrazine. This suspension was then cooled to 60 ° C. and filtered. After washing with water, 1.41 g of residue was obtained. As measured by ICP, platinum was not detected in this alkaline filtrate.

Example  10

The residue obtained from Example 7 was leached at 80-100 ° C. in 600 ml of aqua regia and the Pt content was determined by ICP and found to be 0.22 g.

Claims (14)

A method for recovering a noble metal from a noble metal-containing composition comprising the following process steps:
i) a process for providing a noble metal-containing composition based on an inorganic substance and functionalized by an organic group to contain an adsorbent having at least one precious metal adsorbed thereon;
ii) process steps of sintering the noble metal-containing composition provided in process step i) to obtain an assimilated composition in which the carbon residual content of the noble metal-containing composition is adjusted to a maximum of 10 wt% or less after incineration;
iii) a process step of dissolving the assimilated composition obtained in process step ii) at least partially in an aqueous alkali solution to obtain a noble metal-containing residue;
iv) a process step of dissolving the noble metal-containing residue obtained in process step iii) at least partially in an aqueous solution of oxidizing acid to obtain an aqueous solution of salt of noble metal;
v) process step of recovering the precious metal by optionally reducing the precious metal salt obtained in process step iv). The method according to claim 1, wherein the adsorbent based on the inorganic substance is a silica gel-based or aluminum oxide gel-based adsorbent. The process according to claim 1 or 2, wherein the inorganic adsorbent is functionalized by 0.1 to 1.5 mmol / g of organic groups. The process according to claim 1, wherein the precious metal-containing composition provided in process step i) contains at least 0.5% by weight of the precious metal relative to the total weight of the precious metal-containing composition provided in process step i). . The noble metal-containing composition provided in the process step i) can be obtained by contacting a noble metal-containing residue with an adsorbent functionalized by an organic group and based on an inorganic substance. Way. The process according to claim 1, wherein the precious metal-containing composition provided in process step i) is aerated at temperatures above 700 ° C. in process step ii). The process according to claim 6, wherein the precious metal-containing composition provided in process step i) is aerated for a period of at least 2 hours in process step ii). 8. The process according to claim 1, wherein at least a portion of the assimilated composition obtained in process step ii) is dissolved in an aqueous alkaline solution in the presence of a reducing agent in process step iii) to obtain a noble metal-containing residue. 9. How to get. The method of claim 8, wherein the reducing agent is an organic reducing agent, hydrazine or hydrogen gas. 10. The method of claim 9, wherein the organic reducing agent is selected from the group consisting of formic acid or formate, formaldehyde, alcohol, ascorbic acid, glucose, gluconic acid, ascorbic acid and oxalic acid. The process according to any one of the preceding claims, wherein the noble metal-containing residue obtained in process step iii) is reduced in the hydrogen stream before process step iv). The process according to claim 1, wherein the precious metal-containing residue obtained in process step iii) has a total mass loss of more than 90% relative to the material used in process step i). The method of claim 12, wherein the total mass loss is greater than 95%. The hydrochloric acid according to any one of claims 1 to 13, wherein the noble metal-containing residue obtained in process step iii) is obtained at least partially in nitric acid as an aqueous solution of oxidizing acid to obtain an aqueous solution of salt of the precious metal in process step iv). A method of dissolving a mixture containing pernitric acid in hydrochloric acid containing chlorine gas or hydrochloric acid containing chlorate.